Measuring electrode and measuring system for chemical liquid

ABSTRACT

A measuring electrode for chemical liquid in semiconductor process that measures a chemical liquid used for a semiconductor process comprises a first body having a first internal liquid chamber into which a first internal liquid is filled, and a flow tube for a part or all of which a responsive glass is used and that forms a flow channel where a chemical liquid as being a measuring object flows, wherein the flow tube is so arranged to penetrate the first body and the responsive glass makes contact with the first internal liquid in the first internal liquid chamber.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/690,255, entitled MEASURING ELECTRODE AND MEASURING SYSTEM FORCHEMICAL LIQUID, filed Apr. 17, 2015, which in turn claims priority toJapanese Patent Application Nos. 2014-086109, 2014-086106, 2014-086107,and 2014-086108, each filed Apr. 18, 2014. Each of these applications ishereby incorporated by reference in its entirety for all purposes.

FIELD OF THE ART

This invention relates to a measuring electrode and a measuring systemused for measuring a pH of a chemical liquid used for a cleaningsolution in a semiconductor process.

BACKGROUND ART

A pH of a chemical liquid such as a cleaning solution used in asemiconductor process is measured in order to verify a cleaning effectof the chemical liquid. For example, a pH measuring device described inthe patent document 1 samples and stores a chemical liquid used in asemiconductor manufacturing process and electrochemically measures a pHvalue by immersing a measuring electrode in the chemical liquid. Thechemical liquid sampled by this measuring device is discarded after themeasurement.

However, in accordance with this arrangement, there is a problem that aloss of the chemical liquid increases because the chemical liquid isstored in a measurement container and a considerable amount of thechemical liquid is required to be sampled for measurement.

PRIOR ART DOCUMENT Patent Document

Patent document 1: Japanese Unexamined Patent Application PublicationNo. 2013-142591

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

The present claimed invention intends to solve all of the problems and amain object of this invention is to decrease a used amount of anobjective liquid in measuring a pH of the objective liquid by the use ofthis kind of the measuring electrode.

Means to Solve the Problems

More specifically, a measuring electrode for chemical liquid used insemiconductor process in accordance with this invention is a measuringelectrode for chemical liquid in semiconductor process to measure achemical liquid used in a semiconductor process and comprises a bodyhaving an internal liquid chamber into which an internal liquid isfilled and a flow tube for a part or all of which a responsive glass isused and that forms a flow channel where the chemical liquid as being ameasuring object flows, and is characterized by that the flow tube isarranged in the body so as to make the responsive glass of the flow tubecontact with the internal liquid in the internal liquid chamber.

In accordance with this arrangement, since an electrochemicalmeasurement is conducted while the chemical liquid (hereinafter alsocalled as the measuring liquid) as being the measuring object is flownin the flow tube without storing the chemical liquid in a storage, it ispossible to reduce an amount of the chemical liquid that is used for themeasurement and that is discarded after the measurement by making theflow tube thin or by limiting a flow rate of the chemical liquid thatflows in the flow tube. As a result of this, it is possible todramatically minimize a loss of the chemical liquid compared with thechemical liquid used by a conventional arrangement.

In addition, the measuring system in accordance with this inventioncomprises a chemical liquid flow control mechanism that controls thechemical liquid flowing in the flow tube, and the chemical liquid flowcontrol mechanism halts the flow of the chemical liquid at a time ofmeasuring the chemical liquid.

In accordance with this arrangement, since the flow of the chemicalliquid is halted when, for example, an electromotive force of thechemical liquid is measured in the electrochemical measurement, it ispossible to further lessen the used amount of the chemical liquid sothat the loss of the chemical liquid can be decreased. In addition, alsoin case of measuring the electromotive force by halting the flow of thechemical liquid, if the flow tube is thin, the measurement is notaffected by a convection current of the chemical liquid so that themeasurement accuracy is improved. Furthermore, since the measurement ofthe electromotive force is conducted in a state that the flow of thechemical liquid is halted, it is possible to avoid an influence on themeasurement value due to the flow of the chemical liquid.

The measuring electrode or the measuring system for chemical liquid insemiconductor process in accordance with this invention is characterizedby that the flow tube is in a capillary shape.

In accordance with this arrangement, since the flow tube is formedfurther thinner, it is possible to furthermore reduce the amount of thechemical liquid used for the measurement so that the loss of thechemical liquid can be decreased.

In addition to the above-mentioned invention group 1, this specificationalso describes following invention group 2, invention group 3 andinvention group 4.

(Invention Group 2)

The invention group 2 relates to a measuring system used in anelectrochemical measurement such as a pH measurement, and the measuringliquid is not limited to the chemical liquid used for semiconductorprocess.

A background art and a problem of the invention group 2 are as follows.

An electrochemical measuring device including a pH measuring device bythe use of a glass electrode method comprises a measuring electrode anda reference electrode. Since the internal liquid of the referenceelectrode is diluted when the measuring liquid as being the measuringobject makes contact with the internal liquid of the referenceelectrode, it is necessary to replenish the internal liquid of thereference electrode in order to keep the measurement accuracy. Then, incase that the electrochemical measuring device is used for a long periodof time, for example, about 6 months, it is necessary to replenish theinternal liquid of the reference electrode during this period of time inorder to keep the measurement accuracy. If it is possible to decreasethe replenishing amount of the internal liquid, labor for maintenance ofthe device can be saved.

There are various arrangements as the reference electrode. For example,the reference electrode shown in FIG. 2 in the patent document (UtilityModel Publication of Application No. 59-183655) has an arrangementwherein an internal electrode of the reference electrode extends upwardfrom the bottom end of the reference electrode, the measuring liquidflows in an upper space of the reference electrode, a liquid junction isprovided on an interface between the measuring liquid and the internalliquid, and an internal liquid replenishing port is provided above theupper end of the internal electrode.

With the arrangement of the reference electrode described in this patentdocument, since the internal liquid leaks through the liquid junctionlocating in the upper part of the reference electrode, a replenishingmechanism to replenish the internal liquid is necessary to keep themeasurement accuracy in case of a long term use assumed by thisinvention. However, if the internal liquid is replenished on a constantbasis, there is a problem that the replenishing amount of the internalliquid increases.

The invention group 2 in accordance with the above-mentioned measuringsystem is to solve the above-mentioned problem and a main object is toreduce the replenishing amount of the internal liquid, to keep themeasurement accuracy and to save the labor for maintenance of the devicein the long term use of this measuring system.

A main invention among the invention group 2 invented to solve thisproblem is a measuring system that comprises a body that has an internalliquid chamber into which an internal liquid whose specific gravity isbigger than that of the measuring liquid as being an measuring object isfilled and that is so configured that the internal liquid makes contactwith the measuring liquid flowing above the internal liquid through theliquid junction arranged at the upper end part of the internal liquidchamber, a reference electrode that comprises an internal electrodearranged to contact the internal liquid in the internal liquid chamberand an internal liquid replenishing mechanism that replenishes theinternal liquid into the internal liquid chamber, and is characterizedby that the internal liquid replenishing mechanism replenishes theinternal liquid by a predetermined amount intermittently.

In accordance with this arrangement, since the specific gravity of theinternal liquid is bigger than that of the measuring liquid and theamount of the measuring liquid that flows into the internal liquid sidethrough the liquid junction arranged in the upper end part of theinternal liquid chamber is due to diffusion alone, it is possible toreduce the measuring liquid flowing in because of diffusion and toreduce the amount of the internal liquid that flows out. In addition,since the specific gravity of the internal liquid is bigger than that ofthe measuring liquid, a part of the internal liquid whose concentrationis diluted because the measuring liquid flows in locates in the upperpart of the internal liquid chamber. The internal electrode is arrangedto extend upward from the bottom end part of the internal liquidchamber, even though the internal liquid is intermittently replenishedby means of the internal liquid replenishing mechanism, the dilutedinternal liquid can be replaced by the replenished internal liquid intime before the diluted internal liquid reaches the internal electrode.As a result of this, the concentration of the internal liquid around theinternal electrode can be kept. As mentioned above, since the internalliquid is intermittently replenished, it is possible to make the amountof the internal liquid small to keep the accuracy of the electricpotential measurement.

In addition, the invention group 2 also includes the invention of themeasuring system wherein the internal liquid chamber of the referenceelectrode is so formed that a cross section of the internal liquidchamber at a position locating above the upper end of the internalelectrode and separated from the liquid junction by the predetermineddistance is smaller than a cross section of the internal liquid chamberlocating below the position.

In accordance with this arrangement, since the cross section of theinternal liquid chamber at the position separated from the liquidjunction by the predetermined distance is smaller than the cross sectionof the internal liquid chamber locating below the position, it ispossible to reduce a volume of the internal liquid chamber at a partseparated from the liquid junction by the predetermined distancecompared with a case wherein the cross section is constant in anyposition of the internal liquid chamber. Since the speed of themeasuring liquid flowing in a side of the internal liquid due todiffusion is the same, if the volume of the internal liquid chamberseparated from the liquid junction by the predetermined distance issmaller, in case that the diluted amount of the internal liquid due todiffusion of the measuring liquid is to be replaced, it is possible toreduce a replacing amount of the internal liquid. As a result of this,the amount of the internal liquid to be replaced becomes small so thatthe amount of the internal liquid to be replenished at a time by theinternal liquid replenishing mechanism can be further decreased.

In addition, the invention group 2 also includes the measuring systemwherein the volume of the internal liquid chamber of the referenceelectrode from the liquid junction to the position separated from theliquid junction by the predetermined distance is set to be smaller thanan amount of the internal liquid replenished at a time by the internalliquid replenishing mechanism.

In accordance with this arrangement, in case that the internal liquid isdiluted because the measuring liquid diffuses between the liquidjunction and the position separated from the liquid junction by thepredetermined distance, since an amount of the internal liquid that ismore than an amount corresponding to the diluted amount of the internalliquid is replenished by the internal liquid replenishing mechanism, thediluted part of the internal liquid can be pushed out from the liquidjunction and replaced by the internal liquid securely.

(Invention Group 3)

The invention group 3 relates to a reference electrode used in anelectrochemical measurement device such as a pH measurement device, andthe measuring object is not limited to the chemical liquid used forsemiconductor process.

A background art and a problem of the invention group 3 are as follows.

An electrochemical measuring device including a pH measuring device bythe use of a glass electrode method comprises a measuring electrode anda reference electrode. Since the internal liquid of the referenceelectrode is diluted when the measuring liquid as being the measuringobject makes contact with the internal liquid of the referenceelectrode, it is necessary to replenish the internal liquid of thereference electrode in order to keep the measurement accuracy. Then, incase that the electrochemical measuring device is used for a long periodof time, for example, about 6 months, it is necessary to replenish theinternal liquid of the reference electrode during this period of time inorder to keep the measurement accuracy. If it is possible to decreasethe replenishing amount of the internal liquid, labor for maintenance ofthe device can be saved.

There are various arrangements as the reference electrode. For example,the reference electrode shown in FIG. 2 in the patent document (UtilityModel Publication of Application No. 59-183655) has an arrangementwherein an internal electrode of the reference electrode extends upwardfrom the bottom end of the reference electrode, the measuring liquidflows in an upper space of the reference electrode, a liquid junction isprovided on an interface between the measuring liquid and the internalliquid, and an internal liquid replenishing port is provided above theupper end of the internal electrode.

With the arrangement of the reference electrode described in this patentdocument, since the internal liquid leaks through the liquid junctionlocating in the upper part of the reference electrode, a replenishingmechanism to replenish the internal liquid is necessary to keep themeasurement accuracy in case of a long term use assumed by thisinvention. However, since the internal liquid replenishing port isprovided above the upper end of the internal electrode and near theliquid junction, even though the internal liquid is replenished from theinternal liquid replenishing port, the replenished internal liquid flowsout from the liquid junction. Then in order to replace the internalliquid around the internal electrode, there is a problem that aconsiderable amount of the internal liquid is required to bereplenished.

The invention group 3 in accordance with the above-mentioned measuringsystem is to solve the above-mentioned problem and a main object is toreduce the replenishing amount of the internal liquid, to keep themeasurement accuracy and to save the labor for maintenance of the devicein the long term use of this measuring system using this referenceelectrode.

A main invention among the invention group 3 invented to solve thisproblem is a reference electrode that comprises a body that has aninternal liquid chamber into which an internal liquid is filled and thatis so configured that the internal liquid makes contact with a measuringliquid as being a measuring object flowing above the internal liquidthrough a liquid junction arranged at an upper end part of the internalliquid chamber and an internal electrode that is arranged so as tocontact the internal liquid in the internal liquid chamber, and ischaracterized by that a replenishing port to replenish the internalliquid into the internal liquid chamber is arranged below the upper endpart of the internal electrode.

In accordance with this arrangement, since the internal liquid isreplenished from the replenishing port arranged below the upper end partof the internal electrode, it is possible to replace the liquid aroundthe internal electrode by the replenished internal liquid so that themeasurement accuracy can be kept. In this case, since the internalliquid pushes up and replaces the part where the internal liquid isdiluted due to diffusion of the measuring liquid from the liquidjunction, all needed is just to replenish an amount of the internalliquid corresponding to an amount of the diluted part so that it ispossible to economize and reduce the replenishing amount of the internalliquid.

In addition, the invention group 3 also includes the invention of thereference electrode that is characterized by that a specific gravity ofthe internal liquid is bigger than a specific gravity of the measuringliquid.

In accordance with this arrangement, since the specific gravity of theinternal liquid is bigger than that of the measuring liquid and theamount of the measuring liquid that flows into the internal liquid sidethrough the liquid junction arranged in the upper end part of theinternal liquid chamber is due to diffusion alone, it is possible toreduce the measuring liquid flowing in because of diffusion and toreduce the amount of the internal liquid that flows out. In addition,since the specific gravity of the internal liquid is bigger than that ofthe measuring liquid, a part of the internal liquid whose concentrationis diluted because the measuring liquid flows in locates upper part ofthe internal liquid chamber. Since the internal electrode is arranged toextend upward from the bottom end part of the internal liquid chamber,the diluted part of the internal liquid can be securely pushed up andthe liquid around the internal electrode can be replaced by the internalliquid replenished from the replenishing port locating below the upperend part of the internal electrode. As a result of this, it is possibleto keep the measurement accuracy. With this arrangement, thereplenishing amount of the internal liquid can be economized andreduced.

In addition, the invention group 3 also includes the invention of thereference electrode characterized by that the internal liquid chamber isso formed that a cross section of the internal liquid chamber at aposition locating above the upper end of the internal electrode andseparated from the liquid junction by the predetermined distance issmaller than a cross section of the internal liquid chamber locatingbelow the position.

In accordance with this arrangement, since the cross section of theinternal liquid chamber at the position separated from the liquidjunction by the predetermined distance is smaller than the cross sectionof the internal liquid chamber locating below the position, it ispossible to reduce a volume of a part of the internal liquid chamberfrom the liquid junction to the position separated from the liquidjunction by the predetermined distance compared with a case wherein thecross section is constant in every position of the internal liquidchamber. Since the speed of the measuring liquid flowing in the side ofthe internal liquid due to diffusion is the same, in case that thediluted amount of the internal liquid due to diffusion of the measuringliquid is to be replaced, the volume of the diluted part is small sothat it is possible to reduce a replacing amount of the internal liquid.As a result of this, the replenishing amount of the internal liquid canbe further decreased.

In addition, the invention group 3 also includes an invention of thereference electrode that is characterized by that a volume of a part ofthe internal liquid chamber from the liquid junction to a positionseparated from the liquid junction by the predetermined distance is setto be smaller than an amount of the internal liquid replenished at atime from the replenishing port.

In accordance with this arrangement, in case that the internal liquid isdiluted due to the measuring liquid that diffuses between the liquidjunction and the position separated from the liquid junction by thepredetermined distance, since the internal liquid is replenished by anamount that is more than an amount corresponding to the amount of thediluted internal liquid, it is possible to push up the diluted internalliquid from the liquid junction and to replace the diluted internalliquid securely by the replenished internal liquid.

(Invention Group 4)

The invention group 4 relates to an electrode device comprising ameasuring electrode and a reference electrode used for a pH measurementdevice or the like, and the measuring object is not limited to thechemical liquid used for semiconductor process.

A background art and a problem of the invention group 4 are as follows.

There is a case that a flow injection analysis to measure a pH byobtaining a part of the flowing measuring liquid one after another orcontinuously uses not a polarograph device as shown in the patentdocument (Japanese Unexamined Patent Application Publication No.62-197758) but a grass electrode method. If the pH measurement by theglass electrode method uses the art as described in this invention group1, there might be a case that the internal liquid is contaminated by themeasuring liquid. As a result of this, the measurement accuracy isinfluenced.

A concrete explanation will follow. For example, an example of aconfiguration (not a well-known conventional example) shown in FIG. 6has such a configuration that a pair of internal liquid chambers thathouse an internal liquid and an internal electrode are arranged in abody 202 in a block shape, and one of the pair is a measuring electrode204 and the other is a reference electrode 206.

A flow tube 208 formed by a responsive glass fits into a body 202 of themeasuring electrode 204 in a state of penetrating the internal liquidchamber 204 a of the measuring electrode 204, a through hole 210 thatcommunicates with the flow tube 208 is provided for the body 202 of thereference electrode 206 and the through hole 210 is in communicationwith the internal liquid chamber 206 a of the reference electrode 206through a liquid junction 212.

A measuring liquid 216 flows in a measuring liquid flow channel 214formed by the flow tube 208 and the through hole 210 and a pH of themeasuring liquid 216 is measured by the use of the measuring electrode204 and the reference electrode 206.

A part where the flow tube 208 and the through hole 210 are connected issurrounded and covered by an adhesive or a connecting member 218 such asan O ring or the like so as to connect the flow tube 208 and the throughhole 210 liquid-tightly.

However, in accordance with this arrangement, a measurement error mightbe generated in the reference electrode 206 because of the contaminationwhen the internal liquid 204 b of the measuring electrode 204 enters themeasuring liquid flow channel 214 through a gap between the flow tube208 and the connecting member 218 or a gap between the body 202 and theconnecting member 218 as shown by a wavy line in an enlarged view of theconnecting part due to aged deterioration of the connecting member 218or a contingent careless mistake at a time of initial assembly.

The invention group 4 in accordance with the electrode device is tosolve all of the problems and a main object is to prevent contaminationof the measuring liquid so as to keep the measurement accuracy at a timeof measuring the pH by the electrochemical measurement.

A main invention among the invention group 4 invented to solve thisproblem is an electrode device that comprises a measuring electrode anda reference electrode wherein the measuring electrode comprises a firstbody that forms a first internal liquid chamber that houses a firstinternal liquid and a first internal electrode and a flow tube for apart or all of which a responsive glass is used and that is insertedinto the first body so as to pass the first internal liquid chamber,wherein the measuring liquid as being a measuring object that flows inthe flow tube is supplied to the reference electrode, and ischaracterized by that an output end side of the flow tube connected tothe reference electrode projects from the first body and an area of theprojecting part that extends over the predetermined length is exposed toa space.

In accordance with this arrangement, even though the first internalliquid leaks from the gap between the first body and the flow tube,since a space exposed area provided in the output end side of the flowtube blocks the first internal liquid from being transmitted to thereference electrode, it is possible to prevent the internal liquid (thefirst internal liquid) of the measuring electrode from mixing into theflow channel where the measuring liquid flows in the reference electrodesecurely so that the measurement accuracy of the electric potential canbe kept.

In order to hold the projecting part of the flow tube with ease asub-body that is arranged separately from the first body is furtherprovided and the space is arranged between the first body and thesub-body. It is preferable that a part of the flow tube bridges thespace.

In order to securely hold the flow tube and to prevent the flow tubefrom being bent or broken because a contingent bending force is applied,it is preferable to further comprise a connecting body that connects thefirst body and the sub-body.

It is further preferable that a connecting port connected with thereference electrode is formed on the sub-body.

As a concrete embodiment of a reference electrode that is useful fordownsizing or for reducing a consumed amount of the measuring liquidrepresented is an arrangement wherein the reference electrode comprise asecond internal liquid chamber into which a second internal liquid isfilled and a second body that forms a second flow channel where themeasuring liquid flows, and the measuring liquid in the second flowchannel makes contact with the second internal liquid in the secondinternal liquid chamber through a liquid junction.

In order to hold the projecting part of the flow tube with ease, asecond sub-body that is arranged separately from the second body isfurther provided and the space is arranged between the second body andthe second sub-body. It is preferable that a part of the flow tubebridges over the space.

Furthermore, in order to hold the flow tube securely and to prevent theflow tube from being bent or broken because a contingent bending forceis applied, it is preferable that the reference electrode comprises thesecond connecting body to connect the second body and the secondsub-body.

In addition, it is preferable that the flow tube is formed by connectinga plurality of flow tube elements.

As a concrete embodiment of connecting a plurality of flow tubeelements, it is preferable that on one end part of the other flow tubeelement fits over one end part of one flow tube element and a part whereeach flow tube element fits is tightened by a ring-shape tighteningmember.

More concretely, the tightening member is a ferrule and a fitting memberthat is arranged to make an abutting contact with the ferrule and tofits into the first body connects each of the flow tube elements by theferrule that presses the part where the flow tube elements fit eachother.

In addition, when the first internal liquid leaks from a gap between thefirst body and the flow tube, it is preferable that a part of the spaceis open in order to discharge the first internal liquid from the spacewithout storing the first internal liquid.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a general schematic view of a measuring system in accordancewith one embodiment of this invention.

FIG. 2 is a schematic view of an electrode device in this embodiment.

FIG. 3 is a schematic view showing a pH measurement sequence inaccordance with one embodiment of this invention.

FIG. 4 is a schematic view of an electrode device in accordance withanother embodiment of this invention.

FIG. 5 is a partial enlarged view of an electrode device in accordancewith a further different embodiment of this invention.

FIG. 6 is a schematic view of an electrode device in accordance with afurther different embodiment of this invention.

BEST MODES OF EMBODYING THE INVENTION

On embodiment of this invention will be explained with reference todrawings.

First Embodiment

FIG. 1 shows a measuring system 100 in accordance with this embodiment.

The measuring system 100 is to continuously monitor a concentration of ahydrogen ion of a chemical liquid (hereinafter also called as “ameasuring liquid”) used in a semiconductor manufacturing process suchas, for example, cleaning of a wiring process, Cu plating, and CMP(chemical mechanical polishing), and comprises an electrode device 7 tomeasure a pH of the measuring liquid 9, a measuring liquid flow controlmechanism 3 to flow the measuring liquid 9 in the electrode device 7, aninternal liquid replenishing mechanism 5 to replenish an internal liquid(hereinafter also called as “a second internal liquid”) such as a KCLsolution to the electrode device 7, and an informationprocessing/control mechanism 19 to be connected to the electrode device7, the measuring liquid flow control mechanism 3 and the internal liquidreplenishing mechanism 5 and to transfer measurement data or a controlcommand signal therebetween.

The measuring system 100 can also measure, for example, an ionicconcentration of sodium and an ionic concentration of potassium, and agas concentration of carbon dioxide (pCO2) and a gas concentration ofoxygen (pO2) in addition to a concentration of a hydrogen ion.

The electrode device 7 comprises, as shown in FIG. 2, a measuringelectrode 4 for chemical liquid in semiconductor process (hereinafteralso called just as the measuring electrode 4), a reference electrode 6and a frame body 23 that houses the measuring electrode 4 and thereference electrode 6.

The measuring electrode 4 comprises a body (a body described in claim 1,and hereinafter called as “a first body 54”) having an internal liquidchamber (an internal liquid chamber described in claim 1, andhereinafter called as “a first internal liquid chamber 52”) into which apredetermined internal liquid (an internal liquid described in claim 1,and hereinafter called as “a first internal liquid 50”) such as a pHbuffer solution and an internal electrode (M) mounted to extend upwardfrom a lower part of the first body 54 in the internal liquid chamber52.

The first body 54 is made of a material such as PVC (polyvinylchloride), PP (polypropylene) and PVDF (polyvinylidene fluoride), andcomprises a main member 54 a in a vertically extending rectangularcylindrical shape whose top surface is closed and whose bottom surfaceis open and a cap body 54 b that closes the bottom surface opening ofthe main member 54 a. The first internal liquid chamber 52 formed insideof the first body 54 has a constant cross-sectional shape (for example,a cylindrical shape) from, for example, the bottom end to apredetermined height and only the upper end part is in a conical shapewhose cross section gradually narrows toward an upper part.

The internal electrode (M) comprises, for example, a silver/silverchloride electrode, and is mounted with a bottom end part of theinternal electrode (M) penetrating the cap body 54 b and stands from thecap body 54 b extending upward in the first internal liquid chamber 52.In addition, a point of contact is provided on the bottom end of theinternal electrode (M) so as to make it possible to take an electriccurrent (a voltage) signal out to the outside. The internal electrode(M) is not limited to an arrangement wherein the bottom end part extendsfrom the cap body 54 b, and may extend from a side surface of the mainmember 54 a upward obliquely or in a shape of, for example, an “L”character in the first internal liquid chamber 52.

Furthermore, in this embodiment, the electrode device 7 comprises a flowtube 58 where the measuring liquid 9 flows.

Whole of the flow tube 58 is formed by a responsive glass that respondsto the hydrogen ion and forms a first flow channel 62 where the chemicalliquid flows. The responsive glass contains a predetermined amount ofscandium. A shape of the flow tube 58 is capillary, in other words, alength of the flow tube 58 is sufficiently long relative to an innerdiameter of the flow tube 58, and the flow tube 58 is extremely thin,for example, the inner diameter is about 0.1 mm to 2 mm, preferablyabout 0.5 mm to 1 mm. In addition, a thickness of the flow tube 58 isabout 0.1 mm to 1 mm, and preferably about 0.2 mm. If the thickness isabout 0.2 mm, the responsive glass has high responsiveness. Furthermore,an outer diameter of the flow tube 58 is about 0.3 mm to 4 mm, andpreferably about 1 mm to 2 mm.

The flow tube 58 is arranged to horizontally penetrate the first body 54at the upper end part of the first body 54 and to be immersed in thefirst internal liquid 50 in the first internal liquid chamber 52. Moreconcretely, the flow tube 58 is arranged to penetrate a part of thefirst internal liquid chamber 52 whose cross section is constant andthat locates above the upper end part of the internal electrode (M).

The responsive glass may be used for a part of the flow tube 58 that isimmersed into the first internal liquid 50.

Next, the reference electrode 6 will be explained by the use of FIG. 2.

The reference electrode 6 comprises a second body 42 (a body of thereference electrode described in claim 1) having an internal liquidchamber (an internal liquid chamber of the reference electrode describedin claiml, and hereinafter called as “a second internal liquid chamber”)into which a second internal liquid 15 is filled, an internal electrode(R) mounted to extend upward from a lower part of the second body 42 ina second internal liquid chamber 36 and a replenishing port 17 that isformed in the second body 42 and in communication with the secondinternal liquid chamber 36 to replenish the second internal liquid 15.

Similar to the first body 54 of the measuring electrode 4, the secondbody 42 is made of a material such as PVC, and comprises a main member42 a in a vertically extending rectangular cylindrical shape whose topsurface is closed and whose bottom surface is open and a cap body 42 bthat closes the bottom surface opening of the main member 42 a.

The second internal liquid chamber 36 arranged in the second body 42 isformed to have a cross section of a position both above the upper endpart of the internal electrode (R) and in a predetermined distance (L1)downward from a liquid junction 40 that is smaller than a cross sectionof a position below the position of the predetermined distance (L1).Furthermore, a volume of the second internal liquid chamber 36 from theliquid junction 40 to the predetermined distance (L1) is set to besmaller than an amount of the second internal liquid 15 replenished at atime from the replenishing port 17.

A cross section (a cross section is a circle in this embodiment) of theposition between the liquid junction 40 and the predetermined distance(L1) may be constant or may be varied as far as the cross section issmaller than a cross section of a part below the predetermined position(L1). The cross section of the part below the predetermined distance(L1) may be similarly constant or varied.

Furthermore, in this embodiment, the second flow channel 64 where themeasuring liquid 9 flows is formed in the second body 42. The secondflow channel 64 is formed horizontally at the upper end part of thesecond body 42, and is so configured that the second internal liquid 15contacts the measuring liquid 9 flowing in the second flow channel 64through the liquid junction 40 formed by minute bores arranged at theupper end part of the second internal liquid chamber 36.

The internal electrode (R) comprises, for example, a silver/silverchloride electrode, and is mounted with a bottom end part of theinternal electrode (R) penetrating the cap body 42 b and stands from thecap body 42 b extending upward in the second internal liquid chamber 36.In addition, a point of contact is provided on the bottom end of theinternal electrode (R) so as to make it possible to take an electriccurrent (a voltage) signal out to the outside. The internal electrode(R) is not limited to an arrangement wherein the bottom end part extendsfrom the cap body 42 b, and may extend from a side surface of the mainmember 42 a upward obliquely or in a shape of, for example, an “L”character in the second internal liquid chamber 36.

The replenishing port 17 is arranged at a point a little lower than theupper end part of the internal electrode (R) in this embodiment,however, it may be appropriately varied such that the replenishing port17 is arranged at a position further downward, for example, at aposition which makes it possible to replenish the second internal liquid15 from a direction of a bottom part of the second internal liquidchamber 36, or the replenishing port 17 is arranged at a position of acenter or an upper part of the internal electrode (R).

Next, the frame body 23 will be explained by the use of FIG. 2. Theframe body 23 is made of a material such as a resin or a metal in asquare box shape whose upper part opens, and the measuring electrode 4and the reference electrode 6 are fittingly inserted from upward intothe frame body 23.

A contact point 88 with which the bottom end part of the internalelectrode (M) makes contact and a contact point 89 with which the bottomend part of the internal electrode (R) makes contact are arranged on thebottom plate of the frame body 23.

In addition, a flow-in hole 63 to introduce the measuring liquid 9 intothe flow tube 58 that forms the first flow channel 62 is formed on oneside plate of the frame body 23 that makes contact with the measuringelectrode 4, and a flow-out hole 65 to discharge the measuring liquid 9that flows in the second flow channel 64 is formed on the other sideplate of the frame body 23. Furthermore, a flow-in hole 67 to introducethe second internal liquid 15 to the replenishing port 17 is also formedon the other side plate.

As mentioned above, the electrode device 7 comprises the measuringelectrode 4, the reference electrode 6 and the frame body 23, and themeasuring electrode 4 and the reference electrode 6 are housed in theframe body 23 in a state that the flow-in hole 63, the first flowchannel 62, the second flow channel 64 and flow-out hole 65 communicateeach other and furthermore the replenishing port 17 and the flow-in hole67 communicate each other. The measuring electrode 4 and the referenceelectrode 6 are fixed by means of, for example, a screw, not shown indrawings, in a state of being pushed each other. With this arrangement,the first flow channel 62 and the second flow channel 64 tightly attacheach other so as not to leak the measuring liquid 9 from a space betweenthe first flow channel 62 and the second flow channel 64. In order toimprove adherence, an O-ring may be provided between the first flowchannel 62 and the second flow channel 64. In addition, the flow tube 58is fixed to a part where the flow tube 58 penetrates the first body 54in the measuring electrode 4 by means of an adhesive or the like and thepart is sealed so as not to leak the first internal liquid 50 from thefirst internal liquid chamber 52.

Next, the measuring liquid flow control mechanism 3 comprises a flow-inpipe 12 a to introduce the measuring liquid 9 into the electrode device7, a flow-out pipe 12 b to flow the measuring liquid 9 flowing outthrough the electrode device 7 and a flow pump 10 that is arranged at apredetermined position of the flow-in pipe 12 a or the flow-out pipe 12b to introduce and discharge the measuring liquid 9, and controls theflow of the measuring liquid 9.

The flow-in pipe 12 a is so arranged that a distal end part of theflow-in pipe 12 a is inserted into the flow-in hole 63 of the frame body23 and connected with the flow tube 58 of the measuring electrode 4 andthe measuring liquid 9 is injected from a proximal end part of theflow-in pipe 12 a. The distal end part of the flow-in pipe 12 a and theflow tube 58 of the measuring electrode 4 are connected so as to betightly attached each other by an adhesive or the like so as tointroduce the measuring liquid 9 into the measuring electrode 4 withoutleakage.

The flow-out pipe 12 b is so arranged that a proximal end part of theflow-out pipe 12 b is inserted into the flow-out hole 65 of the framebody 23 and connected with the second flow channel 64 of the referenceelectrode 6 and the measuring liquid 9 is discharged from a distal endpart of the flow-out pipe 12 b. The proximal end part of the flow-outpipe 12 b and the second flow channel 64 of the reference electrode 6are connected so as to be tightly attached each other by an adhesive orthe like so as to discharge the chemical liquid 9 from the second flowchannel 64 without leakage.

In addition, the flow pump 10 is arranged at a predetermined position ofthe flow-in pipe 12 a or the flow-out pipe 12 b, for example, betweenthe proximal end part and the distal end part of the flow-out pipe 12 b.Due to the operation of the flow pump 10, the measuring liquid 9 flowsin the flow-in pipe 12 a, the measuring electrode 4 and the referenceelectrode 6 successively and flows in the flow-out pipe 12 b and then isdischarged to the outside of the measuring system 100.

Next, the internal liquid replenishing mechanism 5 will be explained bythe use of FIG. 1 and FIG. 2. The internal liquid replenishing mechanism5 comprises a container 16 in which the second internal liquid 15 isstored, a replenishing pipe 20 that connects the container 16 and thereference electrode 6 and that replenishes the second internal liquid 15to the reference electrode 6 and a replenishing pump 18 that is arrangedat a predetermined position of the replenishing pipe 20 and that flowsthe second internal liquid 15. The replenishing pipe 20 is so configuredthat a proximal end part is connected to the container 16 and a distalend part is inserted into the flow-in hole 67 of the frame body 23 andconnected to the replenishing port 17. The distal end part of thereplenishing pipe 20 and the replenishing port 17 of the referenceelectrode 6 are connected so as to be tightly attached each other by anadhesive or the like so as to flow the second internal liquid 15 intothe second internal liquid chamber 36 without leakage. In order toimprove adhesiveness, an O-ring or the like may be provided between thereplenishing pipe 20 and the replenishing port 17.

The replenishing pump 18 is arranged between the proximal end part andthe distal end part of the replenishing pipe 20. Due to the operation ofthis replenishing pump 18, the second internal liquid 15 from thecontainer 16 flows in the replenishing pipe 20 and passes thereplenishing port 17 and then is replenished to the reference electrode6.

Next, the information processing/control mechanism 19 will be explainedby the use of FIG. 1 and FIG. 2. The information processing/controlmechanism 19 comprises a potentiometer 26 to calculate a pH value of themeasuring liquid 9 measured by the electrode device 7, a driver circuit34 comprising a circuit to operate the flow pump 10 and the replenishingpump 18 and a control device 29 that processes the information obtainedby the potentiometer 26 and that comprises a computer to output anoperation signal to the driver circuit 34 and a display. In thisembodiment, the control device 29 is arranged outside of a casing 2. Theinformation processing/control mechanism 19 itself may be arrangedoutside of the casing 2.

The potentiometer 26 is electrically connected to the internal electrode(M) of the measuring electrode 4 and the internal electrode (R) of thereference electrode 6 in the electrode device 7 by a wire 22 of theinternal electrode (M) and a wire 24 of the internal electrode (R)through the contact points 88, 89. With this arrangement, a potentialdifference between the internal electrode (M) and the internal electrode(R) is measured by means of the potentiometer 26 based on each electricpotential detected by the internal electrode (M) and the internalelectrode (R). The potentiometer 26 is electrically connected to thecontrol device 29 through an external connecting terminal 28, and thecontrol device 29 calculates the pH value of the measuring liquid 9based on an output value of the potentiometer 26 by means of thecomputer and displays the calculated value on the display. Thecalculated pH value is stored in a memory media of the computer and canbe displayed when necessary.

The driver circuit 34 is electrically connected to the flow pump 10 andthe replenishing pump 18 through wires 30, 32, and the driver circuit 34is electrically connected to the control device 29 through the externalconnecting terminal 28. The driver circuit 34 controls operation or haltof the flow pump 10 and the replenishing pump 18 based on the signalfrom the computer of the control device 29 and adjusts a timing and anamount of the measuring liquid 9 flowing in the electrode device 7. Inaddition, the amount of the second internal liquid 15 to replenish orthe timing to replenish the second internal liquid 15 is controlled soas to make it possible to continuously operate the measuring system 100for several months, for example, about 4 months to 8 months.

Next, a measuring sequence of the pH measurement of the measuring liquid9 by using this measuring system 100 will be explained by the use ofFIG. 3. A line of P1 indicates ON and OFF of the operation of the flowpump 10. Similarly, P2 indicates ON and OFF of the replenishing pump 18.

After correction of the measuring electrode 4 and the referenceelectrode 6 is conducted (not shown in drawings), the measurement isinitiated. First, a measurement 1 will be explained. During themeasurement 1, the flow pump 10 (P1) of the internal liquid replenishingmechanism 5 is operated during a predetermined period of time by theinformation processing/control mechanism 19 to flow the measuring liquid9 in the flow-in pipe 12 a and the flow-out pipe 12 b so as to flow themeasuring liquid 9 into the measuring electrode 4 and the referenceelectrode 6. An amount of the measuring liquid 9 introduced at this timeis, for example, about several hundred μL. After the measuring liquid 9flows in the measuring electrode 4 and the reference electrode 6, theflow pump 10 is once halted. At this time, the pH is measured.

As mentioned above, a process of operating and halting the flow pump 10and of measuring the pH in the measurement 1 is considered to be onetime measurement and this process is repeated at “n” times, namely themeasurement of the pH is conducted by continuously repeating the processat, for example, 50 to 200 times. After the pH is measured, the flowpump 10 is halted by the information processing/control mechanism 19 andthen the replenishing pump 18 (P2) is operated for a predeterminedperiod of time so that the second internal liquid 15 such as a KCLsolution or the like is replenished from the container 16 to the secondinternal liquid chamber 36 of the reference electrode 6 by apredetermined amount. The replenishing amount of the second internalliquid is an amount that can replace a part where the concentration ofthe second internal liquid 15 is diluted because the measuring liquid 9flows in from the liquid junction 40 in the reference electrode 6. Forexample, about several tens μL of the second internal liquid isreplenished.

“N” times of the measurement and the replenishment of the secondinternal liquid 15 are set to be one measurement routine, and the secondinternal liquid 15 is replenished periodically by repeating thismeasurement routine. After completion of the measurement routine that isrepeated at a desired number of times, the pH measurement is terminated.

Since the measuring electrode 4 has an above-mentioned arrangement, itis possible to measure the electrical potential by flowing the measuringliquid 9 in the capillary shaped flow tube 58, resulting in reducing theamount of the measuring liquid 9 used for the measurement. With thisarrangement, it is possible to decrease an amount of the chemical liquidthat is discarded after the measurement. Especially, in case that theelectric potential is measured when the flow of the measuring liquid 9is halted by halting the flow pump 10, it is possible to furtherdecrease the used amount of the chemical liquid.

In addition, even though a case that a temperature of the measuringliquid 9 is high, for example, about 50° C., since the temperature ofthe measuring liquid 9 drops while the measuring liquid 9 flows in theflow tube 58, no convection current occurs in the flow tube 58 eventhough the flow pump 10 is halted. As a result of this, it is possibleto prevent dispersion of the measured electric potential due to theconvection current so that the accuracy of the electric potentialmeasurement can be improved. In addition, since the flow pump 10 ishalted, the pH is measured by the measuring electrode 4 and thereference electrode 6 in a state that the flow of the chemical liquid isstopped. As a result of this, it is possible to avoid the influence onthe pH value due to the flow of the chemical liquid.

In addition, in this embodiment, since the flow tube 58 is arrangedabove the upper end part of the internal electrode (M) and to pass apart of the first internal liquid chamber 52 having the constant crosssection, air bubbles generated around the flow tube 58 due to the pHmeasurement do not attach to the flow tube 58 and are collected in theupper part of the first internal liquid chamber 52. With thisarrangement, it is possible to prevent degradation of the measurementaccuracy due to the air bubbles. In this embodiment, the upper end partof the first internal liquid chamber 52 is formed in a conical shapewherein the upper, the more the cross section decreases, however, it isnot limited to this. The upper surface of the first internal liquidchamber 52 may be in a flat shape or a hemisphere as long as a space tohold the air bubbles is formed above the flow tube 58.

In addition, since the responsive glass of the flow tube 58 is made of amaterial containing a predetermined amount of Scandium, it has ahydrofluoric acid resistance. As a result of this, since it is difficultto be eroded even though the chemical solution to be measured is strongacidity containing hydrofluoric acid, the flow tube 58 can be used for along period of time.

In addition, since the reference electrode 6 has the above-mentionedarrangement, it is possible to replenish the second internal liquid 15from the replenishing port 17 locating below the upper end part of theinternal electrode (R) and to replace the liquid around the internalelectrode (R) with the second internal liquid 15 so that the measurementaccuracy can be maintained. In this case, since the part of the secondinternal liquid 15 diluted by the measuring liquid 9 that flows in fromthe liquid junction 40 is pushed up and replaced by the second internalliquid 15, only the amount of the second internal liquid 15corresponding to the diluted amount is required to be replenished sothat it is possible to economize and reduce the replenishing amount ofthe second internal liquid 15.

The position of the replenishing port 17 may be appropriately varied.The replenishing port 17 may locate at a further downward position, inother words, at a bottom end part of the second internal liquid chamber36. In this case, even though a case that a specific gravity of thesecond internal liquid 15 is smaller than that of the measuring liquid9, since the replenishing port 17 locates at a position farthest fromthe liquid junction 40, the replenished second internal liquid 15 willnot flow out from the liquid junction 40 and it is possible to replacethe liquid around the internal electrode (R) securely with the amount ofthe second internal liquid 15 corresponding to the amount diluted by themeasuring liquid 9 that flows in from the liquid junction 40 so that thereplenishing amount of the second internal liquid 15 can be economized.

In addition, in case that the specific gravity of the second internalliquid 15 is bigger than that of the measuring liquid 9, thereplenishing port 17 may locate above the upper end part of the internalelectrode (R). In this case, since the specific gravity of the secondinternal liquid 15 is bigger than that of the measuring liquid 9, anamount of the second internal liquid 15 that flows out to a side of themeasuring liquid 9 through the liquid junction 40 immediately after thesecond internal liquid 15 is replenished is small and the secondinternal liquid 15 remains around the internal electrode (R) due to itsown weight. As a result of this, it is possible to keep theconcentration of the second internal liquid 15 around the internalelectrode (R). Furthermore, since the second internal liquid 15 whosespecific gravity is bigger than the measuring liquid 9 is replenished,the part of the second internal liquid 15 diluted by the measuringliquid 9 that flows in from the liquid junction 40 can be pushed upsecurely so that it is possible to replace the liquid around theinternal electrode (R) with the second internal liquid 15. Since it ispossible to make the replenishing amount of the second internal liquid15 correspond to part of the second internal liquid 15 diluted by themeasuring liquid 9 that flows in from the liquid junction 40, thereplenishing amount of the second internal liquid 15 can be economizedand reduced.

In addition, since the internal electrode (R) is arranged to extendupward from the bottom end part of the second internal liquid chamber36, even though the second internal liquid 15 is replenishedintermittently by the replenishing pump 18 of the internal liquidreplenishing mechanism 5 like the above-mentioned measurement sequence,the concentration of the liquid around the internal electrode (R) can bekept by making it possible to replace the second internal liquid 15 intime before the diluted part in the upper part of the second internalliquid chamber 36 reaches the internal electrode (R). As mentioned,since the second internal liquid 15 can be replenished intermittently,it is possible to reduce the replenishing amount of the second internalliquid 15 to the container 16 and to continuously operate this measuringsystem 100 without replenishing the second internal liquid 15 for a longperiod of time, for example, for 4 months to 8 months.

Although it is also possible to operate the replenishing pump 18 to flowan extremely subtle amount of the second internal liquid 15 withoutcompletely stopping the replenishing pup 18 so as to replenish thesecond internal liquid 15 by the amount that corresponds to the dilutedamount due to the measuring liquid 9 that flows in at predetermined timeintervals, it is preferable to completely halt the replenishing pump 18during the pH measurement.

Furthermore, since the cross section in the predetermined distance (L1)from the liquid junction 40 is smaller than the cross section of thelower part than the predetermined distance (L1), the part in thepredetermined distance (L1) becomes thinner than the part locating theinternal electrode (R) so that it is possible to further reduce theamount of the part where the second internal liquid 15 is diluted by themeasuring liquid 9 that flows in from the liquid junction 40. As aresult of this, the amount of the part of the second internal liquid 15to be replaced becomes less so that it is possible to further reduce thereplenishing amount of the second internal liquid 15.

In addition, the predetermined distance (L1) is variously varieddepending on the measurement condition. For example, a volume of thepart where the second internal liquid 15 is diluted because themeasuring liquid 9 flows in from the liquid junction 40 after conductingthe pH measurement for a predetermined period of time is set to be (V2),and a distance from the liquid junction 40 is set to be (L2). And avolume in the second internal liquid chamber 36 to the predetermineddistance (L1) is set to be (V1), (V1) and (L1) are so set to satisfy therelations of (V2)<(V1) and (L2)<(L1).

The amount of the second internal liquid 15 to be replenished isdetermined based on thus determined predetermined distance (L1) and itsvolume (V1). In this case, if the relation of (V2)<(V3)<(V1) holdsbetween the amount to be replenished (V3) and the distance from theliquid junction 40 (L3), the relation of (L2)<(L3)<(L1) is established.Then it is possible to replace the part diluted by the measuring liquid9 with the second internal liquid 15.

Furthermore, if the replenishing amount (V3) is an amount wherein therelation of (V2)<(V1)<(V3) is satisfied, the relation of (L2)<(L1)<(L3)is established so that the part diluted by the measuring liquid 9 can besufficiently replaced with the second internal liquid 15. Morespecifically, in case that the second internal liquid 15 is dilutedbecause the measuring liquid 9 diffuses in a space between the liquidjunction 40 and the predetermined distance (L1), since an amount of thesecond internal liquid 15 more than the amount corresponding to thediluted amount is replenished, it is possible to push out the dilutedpart from the liquid junction 40 and to replace the diluted part withthe second internal liquid 15 securely.

The volume (V2) of the diluted part and the replenishing amount (V3) ofthe second internal liquid 15 may satisfy at least a relation of(V2)<(V3).

Second Embodiment

Next, a second embodiment of this invention will be explained by the useof FIG. 4. The numerical codes in FIG. 4 that are the same as those inFIG. 2 indicate the same or corresponding configuration as that of theabove-mentioned embodiment.

The electrode device 307 comprises the measuring electrode 304 and thereference electrode 306 as shown in FIG. 4.

The measuring electrode 304 comprises a first body 354 a having a firstinternal liquid chamber 352 into which a first internal liquid 350 isfilled, a sub-body 354 b arranged separately from the first body 354 aand a connecting body 354 c that connects the first body 354 a and thesub-body 354 b. Furthermore, the measuring electrode 304 comprises aninternal electrode (M) mounted to extend upward from a bottom part ofthe first body 354 a in the first internal liquid chamber 352. A body354 of the measuring electrode 304 comprises the first body 354 a, thesub-body 354 b and the connecting body 354 c. A material of the body 354is the same as that of the above-mentioned first body 54. Similar to thefirst body 54, the first body 354 a comprises a main member 354 d and acap body 354 e, and a first internal liquid chamber 352 is formed insideof the main member 354 d.

The sub-body 354 b is a block body generally in a cuboid shape, andarranged separately from the first body 354 a by a predetermineddistance by integrally connecting an upper end part of one side surfaceof the first body 354 a and an upper end part of one side surface of thesub-body 354 b by the connecting body 354 c whose shape is a generallycuboid shape. A space (S1) is formed between the first body 354 a andthe sub-body 354 b each of which is arranged separately with its bottompart open. In this embodiment, similar to the above-mentioned sub-body354 b, another sub-body 354 b is arranged separately from the first body354 a by integrally connecting an upper end part of the other sidesurface of the first body 354 a and an upper end part of one sidesurface of the sub-body 354 b by the connecting body 354 c. Since eachbody is connected, the measuring electrode 304 is formed generally in a“T” character shape in a front view wherein the first body 354 a locatesin the center and the sub-body 354 b is provided in each side throughthe connecting body 354 c.

Furthermore, the sub-body 354 b is provided with a female screw hole 388as a connecting port with the reference electrode 306 and a male screwmember 386 is arranged as being a fitting member to be screwedretractably and fittingly inserted into the female screw hole 388.Furthermore, the female screw hole 388 and the space (S1) are connectedby a communicating hole 380.

Furthermore, in this embodiment, the measuring electrode 304 comprises aflow tube 358 where the measuring liquid 9 flows.

Whole of the flow tube 358 is formed by a responsive glass that respondsa hydrogen ion and forms a first flow channel 362 where the measuringliquid 9 flows. A downstream side of the first flow channel 362 becomesan output end side of the flow tube 358 and an upstream side of thefirst flow channel 362 becomes an input end side of the flow tube 358.The material and the shape of the flow tube 358 are the same as those ofthe flow tube 58 in the first embodiment. In addition, similar to theflow tube 58 that is arranged in the first body 54, the flow tube 358 isarranged in the first body 354 a.

Furthermore, the output end side of the flow tube 358 projects from thefirst body 354 a so as to be inserted into the communicating hole 380 ofthe sub-body 354 b. With this arrangement, a part of the flow tube 358bridges the space (S1) arranged between the first body 354 a and thesub-body 354 b and the part of the flow tube 358 is exposed to the space(S1).

In addition, in this embodiment, the input end side of the flow tube 358also projects from the first body 354 a and the input end side isinserted into the communicating hole 380 formed on the sub-body 354 bseparately arranged from the other side surface of the above-mentionedfirst body 354 a.

The responsive glass may be used for a part of the flow tube 358 that isimmersed in the first internal liquid 350.

A configuration of the reference electrode 306 is the same as that ofthe reference electrode 6 in the above-mentioned embodiment.

Next, a concrete configuration of the electrode device 307 will beexplained. The electrode device 307 is so configured that the flow tube358 and a second flow channel 64 of the reference electrode 306 areconnected by a connecting pipe 382 so that the measuring liquid 9 issupplied to the reference electrode 306 from the measuring electrode304.

Concretely, one end side of the connecting pipe 382 is tightly connectedto the second flow channel 64 by means of adhesive or the like and theother end side of the connecting pipe 382 fits over the output end sideof the flow tube 358 so that a flow channel where the measuring liquid 9flow is formed. Furthermore, a ring-shape member 390 to push a peripheryof the connecting pipe 382 is arranged on an outer fitting part of theconnecting pipe 382. More concretely, the ring-shape member 390 is aring-member such as a ferrule having a tapered surface, and the malescrew member 386 makes an abutting contact with the tapered surface byscrewing the male screw member 386 into the female screw hole 388 sothat the outer fitting part of the connecting pipe 382 is pushed by theferrule and the connecting pipe 382 is fixed to the flow tube 358.

A distal end part of an inflow pipe 12 a is connected to the input endside of the flow tube 358 so as to make the measuring liquid 9 flow inthe flow tube 358 from the inflow pipe 12 a. For example, the distal endpart of the inflow pipe 12 a fits over the input end side of the flowtube 358 and similar to the above-mentioned embodiment, a tighteningmember is arranged at this part so that the inflow pipe 12 a is fixed tothe flow tube 358.

In addition, the part of the first body 354 a where the flow tube 358penetrates is fixed to the flow tube 358 by means of adhesive or thelike and sealed so as not to leak the first internal liquid 350 from thefirst internal liquid chamber 352.

Since the electrode device 307 has the above-mentioned configuration,even though the first internal liquid 350 leaks from the part of thefirst body 354 a where the flow tube 358 penetrates due to the ageddeterioration, the first internal liquid 350 is prevented from beingtransmitted to the reference electrode 306 by a space exposed areaarranged in the output end side of the flow tube 358. As a result ofthis, it is possible to prevent the first internal liquid 350 of themeasuring electrode 304 from mixing into the second flow channel 64where the measuring liquid 9 flows in the reference electrode 306securely. Since the bigger the space exposed area is, the more securelythe first internal liquid is prevented from being transmitted to thereference electrode 306, it is preferable that the predetermined lengthof the projecting part is longer.

In addition, since the measuring electrode 304 comprises the sub-bodies354 b in addition to the first body 354 a, it is possible to hold theprojecting part of the flow tube 358 by the sub-bodies 354 b.

Furthermore, in case that the sub-body 354 b is connected to the firstbody 354 a by the connecting body 354 c, the first body 354 a, thesub-body 354 b and the connecting body 354 c are integrally formed. As aresult of this, the projecting part of the flow tube 358 can be held bythe sub-body 354 b more stably so that it is possible to prevent theflow tube 358 from being broken or cracked due to a contingent bendingstress applied to the flow tube 358.

In addition, a distance between the first body 354 a and the sub-body354 b is determined by a width of the connecting body 354 c thatconnects the first body 354 a and the sub-body 354 b. The distance canbe elongated by increasing the width of the connecting body 354 c. Withthis arrangement, it is possible to make the first internal liquid 350insulated from the reference electrode 306 securely. For example, incase that it is assumed to be that the leakage of the first internalliquid 350 becomes much, this arrangement is preferable.

Furthermore, a female screw hole 388 is arranged as a connecting portbetween the reference electrode 306 and the second flow channel 64 in aside of the sub-body 354 b that contacts the reference electrode 306.With this arrangement, it is possible to supply the measuring liquid 9to the second flow channel 64 securely by tightly connecting the flowtube 385 with the connecting pipe 382.

In addition, the reference electrode 306 may comprise a second sub-bodyand a second connecting body so as to make it possible to hold theprojecting part of the flow tube 358. Concretely, the block shapedsecond sub-body is formed on a side surface of the reference electrode306 to face the measuring electrode 304 through the second connectingbody. As mentioned, a space similar to the above-mentioned space (S1) isformed by arranging the second sub-body separately from the second body42. The flow tube 358 projecting from the first body 354 a is held bythe second sub-body and a part of the flow tube 358 bridges over thespace.

In accordance with this arrangement, since the second body is formed onthe second body 42 of the reference electrode 306 through the secondconnecting body, it is possible to hold the flow tube 358 without beingbroken. In addition, since a part of the flow tube 358 bridges over thespace formed by the second body 42 and the second connecting body, thespace exposed area is provided for the flow tube 358 so that the firstinternal liquid 350 is blocked from being transmitted to the referenceelectrode 306.

Third Embodiment

Next, a third embodiment will be explained by the use of FIG. 5.

The electrode device 407 comprises a measuring electrode 404 and areference electrode 406 as shown in FIG. 5.

Whole of the flow tube 358 of the electrode device 307 in theabove-mentioned embodiment is formed by the responsive glass. A flowtube 458 of the electrode device 407 is formed by a plurality of flowtube elements, each of which is connected, and each of the flow tubeelements comprises a responsive glass tube 458 a whole of which isformed by the responsive glass and an elastic tube 458 b made of resin.More specifically, a part of the flow tube 458 is made of the responsiveglass. An output end side (one end side of the elastic tube 458 b) ofthe flow tube 458 is connected to a second flow channel 464 of thereference electrode 406 so that the measuring liquid 9 is supplied tothe reference electrode 406 from the measuring electrode 404. Inaddition, the reference electrode 406 is so configured that the secondbody 442 has a second internal liquid chamber 436 into which a secondinternal liquid 415 is filled and the second internal liquid 415 makescontact with the measuring liquid 9 that flows in the second flowchannel 464 through a liquid junction 440.

Concretely, the other end part of the elastic tube 458 b fits over oneend part of the responsive glass tube 458 a and the part where theelastic tube 458 b fits over the responsive glass tube 458 a is providedwith a ring-shape tightening member 490 that presses down the part. Moreconcretely, the tightening member 490 is, for example, a conical ferrulehaving a tapered surface, and a male screw member 486 is screwed into afemale screw hole 488 formed on the first body 454 a in a state that themale screw member 486 makes an abutting contact with the taperedsurface. With this arrangement, the male screw member 488 presses theferrule so as to be in a state that the male screw member 488 engageswith the ferrule, and the part where the elastic tube 458 b fits overthe responsive glass tube 458 a is pressed by the ferrule so that theresponsive glass tube 458 a and the elastic tube 458 b are connected.

Since the elastic tube 458 b has an elastic force, when the elastic tube458 b is pressed by the ferrule, the elastic tube 458 b tightly attachesthe responsive glass tube 458 a that is made of a hard responsive glassso that the responsive glass tube 458 a and the elastic tube 458 b areliquid-tightly connected.

In addition, the output end side (one end side of the elastic tube 458b) of the flow tube 458 is also connected to the second flow channel 464by the use of the tightening member 490.

Furthermore, a space (S2) is formed between the measuring electrode 404and the reference electrode 406 arranged separately from the measuringelectrode 404. In case of setting the measuring electrode 404 and thereference electrode 406 in the measuring system 300, even though theposition of setting the measuring electrode 404 and the referenceelectrode 406 is misaligned, it is possible to absorb the positionaldisplacement by the elastic tube 458 b that is soft so that assemblingthe electrode device 407 becomes easy.

Since the electrode device 407 has the above-mentioned configuration,similar to the electrode device 307, it is possible to prevent the firstinternal liquid 450 filled in the first internal liquid chamber 452 frommixing into the first flow channel 462 as being a flow channel of themeasuring liquid 9 so that an accuracy of measuring the electricpotential can be kept.

The tightening member 490 may not be used, and the responsive glass pipe458 a and the elastic tube 458 b may be connected by tightly attachingone end part of the responsive glass pipe 458 a projecting from thefirst body 454 a to the other end part of the elastic tube 458 b byadhesive or the like. Furthermore, the output end side of the flow tube458 also may be connected with the second flow channel 464 in a tightlyattached state by the adhesive or the like.

Instead of the elastic tube 458 b, a hard pipe may be connected to theresponsive glass pipe 458 a to constitute the flow tube 458 and thespace (S2) is formed.

Furthermore, similar to the measuring electrode 304, the measuringelectrode 404 or the reference electrode 406 may comprise the sub-bodyand the connecting body so as to form the space (S2) to hold the flowtube 458.

For example, in case of measuring not only the concentration of hydrogenbut also the concentration of, for example, a sodium ion or a potassiumion simultaneously, a plurality of measuring electrodes may be arrangedin parallel tailored to a kind of the ions to be measured so that thechemical liquid flowing out from the measuring electrode is merged andthe reference electrode may be used in common. Alternatively, aplurality of measuring electrodes may be arranged in serial to measurethe hydrogen ion, the sodium ion and the potassium ion in order and thereference electrode may be arranged further in serial and the referenceelectrode may be used in common. In accordance with this arrangement, itis possible to downsize the measuring system and to measure a pluralityof ionic concentrations simultaneously.

In addition, as the measuring liquid as being the object to be measuredis not limited to the chemical liquid used in the semiconductormanufacturing process. For example, since most of chemical liquids ormaterial solutions used for food manufacture, medicine manufacture,medical equipment and cell culture is expensive with a small amount, theeffect of this invention that the sample amount necessary to measure issmall is especially remarkable. It is possible to apply this inventionalso to a general waste water treatment, a general water treatment, anindustrial waste water treatment, an industrial water treatment,electric power generation, an automotive industry, an electric apparatusindustry, a petrochemical industry, a metalworking industry, a resinprocessing industry, an environmental water quality analysis and achemical plant.

In addition, this invention is not limited to the above-mentionedembodiments, and may be variously modified without departing from aspirit of the invention and a part or all of the above-mentionedembodiments or the modified embodiment may be appropriately combined.

EXPLANATION OF CODES

-   -   100 . . . measuring system    -   4, 304, 404 . . . measuring electrode    -   6, 306, 406 . . . reference electrode    -   7, 307, 407 . . . electrode device    -   10 . . . flow pump    -   17 . . . replenishing port    -   18 . . . replenishing pump    -   36 . . . second internal liquid chamber    -   40 . . . liquid junction    -   42 . . . second body    -   52 . . . first internal liquid chamber    -   54 . . . first body

1. A measuring system comprising; a reference electrode including (i) abody having an internal liquid chamber into which an internal liquidwhose specific gravity is greater than that of the measuring liquid asbeing a measuring object is filled and being configured so that theinternal liquid makes contact with the measuring liquid flowing abovethe internal liquid through the liquid junction arranged at the upperend part of the internal liquid chamber and (ii) an internal electrodearranged to contact with the internal liquid in the internal liquidchamber, and an internal liquid replenishing mechanism replenishing theinternal liquid into the internal liquid chamber, wherein the internalliquid replenishing mechanism replenishes the internal liquid by apredetermined amount intermittently.
 2. The measuring system accordingto claim 1, wherein the internal liquid chamber of the referenceelectrode is formed so that a cross section of the internal liquidchamber at a position locating above the upper end of the internalelectrode and separated from the liquid junction by the predetermineddistance is smaller than a cross section of the internal liquid chamberlocating below the position.
 3. The measuring system according to claim2, wherein the volume of the internal liquid chamber of the referenceelectrode from the liquid junction to the position separated from theliquid junction by the predetermined distance is set to be smaller thanan amount of the internal liquid replenished at a time by the internalliquid replenishing mechanism.